Method for scheduling transmissions in communication systems

Abstract

A method for scheduling transmissions to a plurality of users in a communication network determines a satisfaction metric and a dissatisfaction metric for each user in a given timeslot that is to be used for a next scheduled transmission to one of the users. Each user is assigned a weight based on a value of at least one of the user's satisfaction metric, the user's dissatisfaction metric and a rate requested by the user. The use having the highest weight is selected to be served the next scheduled transmission in the given timeslot.

1. A method for scheduling transmissions to a plurality of users so as to enforce a minimum throughput constraint in a communication network, comprising:
 determining for each user in a given timeslot a dissatisfaction metric based on a channel quality, the dissatisfaction metric being a token count of a token counter that tracks an achieved performance relative to a target minimum throughput for each user; 
 computing a first weight function for each user based on a rate requested by each user, an exponential function of the dissatisfaction metric and a quality of service class for each user; 
 computing a second weight function for each user based on the rate requested by each user; and 
 scheduling at least one user in a given timeslot to be served in a next scheduled transmission based on the first and second weight functions. 
 
     
     
       2. The method of  claim 1 , wherein the token counter is decremented when each user is scheduled and incremented at each user's target minimum throughput. 
     
     
       3. The method of  claim 1 , wherein the first weight function of each user is defined by
     w   i   1 = DRC   i   1+δ   ·e   aT     i     (n) , 
 
       where DRCi denotes the rate requested by the ith user, δ represents a rate request exponent, a denotes a tunable parameter and Ti denotes the dissatisfaction metric for the ith user; and
 the second weight function is defined by
     w   i   2   =DRC   i . 
 
 
     
     
       4. The method of  claim 1 , wherein the target minimum throughput is a function of at least one of a quality of service (QoS) class assigned by the network to each user and a QoS class requested by each user at the start of a data session. 
     
     
       5. A method for scheduling transmissions to a plurality of users so as to enforce a maximum throughput constraint in a communication network, comprising:
 determining, for each user in a given timeslot a satisfaction metric based on a channel quality, the satisfaction metric being a token count of a token counter that tracks an achieved performance relative to a target maximum throughput for each user; 
 computing a first weight function if the determined satisfaction metric is 0 or greater; 
 computing a second weight function if the determined satisfaction metric is negative, the second weight function being based on a rate requested by each user, an exponential function of the dissatisfaction metric and a quality of service class for each user; and 
 scheduling at least one of said plurality of users in the given timeslot to be served in a next scheduled transmission based on the sign of the satisfaction metric, while enforcing maximum throughput constraints for said plurality of users. 
 
     
     
       6. The method of  claim 5 , further comprising:
 maintaining a token counter for each user that tracks each user's achieved performance relative to the target maximum throughput of the user. 
 
     
     
       7. The method of  claim 6 , wherein the token counter for each user is incremented as a function of each user's target maximum throughput in each slot, and decremented by the number of bits transmitted when each user is scheduled. 
     
     
       8. The method of  claim 5 , wherein said second weight function is defined by
     w   i   =DRC   i   1+δi   ·e   aiT     i     R     max   , 
 
       where DRCi denotes the rate requested by the ith user, δ represents a rate request exponent, a i  denotes a tunable parameter and T i   R     max    represents the satisfaction metric for the ith user. 
     
     
       9. The method of  claim 8 , wherein said scheduling further includes selecting a user of the plurality of users having a highest positive resultant weight function to be served during a next scheduled transmission, else idling the given timeslot of the next scheduled transmission. 
     
     
       10. The method of  claim 5 , wherein the target maximum throughput is a function of at least one of a quality of service (QoS) class assigned by the network to each user and a QoS class requested by each user at the start of a data session.